24 



THE VENOIM OP HELODERMA. 



In the central duct the epithelium is one cell-layer thick and is thrown into a 

 series of low undulations. In form the cells are columnar and, as Holm 

 notices, are of slightly smaller dimensions than the intralobular tubule cells. 

 According to Holm, there is no granulation in their protoplasm, but this is not 

 strictly true, judging, at least, from some of my preparations — preparations 

 which in other respects are perfectly satisfactory, and therefore probably reli- 

 able in regard to this point also. These preparations show that in nearly all of 

 the collecting-duct cells the peripheral portion of the cytoplasm is crowded with 

 exceedingly minute granules, the crowding being so dense that under ordinary 

 magnification {i. c, i inch obj.) the whole appears as a hyaline mass. These 

 granules are totally unlike the large, clearly defined granules of the intra- 

 lobular tubules; they are much smaller than the latter, do not stain at all with 



Fig. 9. — Section of portion of normal lobule, showing terminal acini, and several intralobular ducts. Note clear 

 alveolar character of protoplasm in cells of peripheral acini and presence of granules in many cells of 

 intralobular ducts (Zeiss oc. 2, obj. DD.). 



iron hematoxylin, and absorb cytoplasmic stains only slightly. The nuclei of 

 these cells are confined to their basal portion, where they are embedded in a 

 rather compact mass of ordinary cytoplasm (fig. 11). 



According to Holm, the central collecting-duct cells have no secretory 

 functions. I am inclined to concur in this view, although I have observed cells 

 which show faint traces of secreting. I have, for instance, frequently seen 

 small granular threails extending out from the cells into the lumen of the duct, 

 but it is possible that these may have been forced out of the cells hy the pres- 

 sure incident to the excision of the gland. 



The cells of the intralobular tubules are columnar, but are more capacious 

 than those of the central collecting duct (fig. 10). They are the typical 

 granule-secreting cells. The entire inner portion of the cells bordering the 

 lumen, including in average cases from one-half to four-fifths of their extent 



